The lck gene product, p56.sup.lck, is a member of the src family of protein tyrosine kinases. Cooper, J. A. (1990) in Peptides and Protein Phosphorylation (Kemps, B. E., ed) pp. 85-113, CRC Press, Boca Raton, Fla. The lck protein is normally expressed in T lymphocytes and natural killer cells, where it likely performs a variety of functions relating to signal transduction through ligand binding to selected surface proteins. Bolen, J. A., and Veillette, A. (1989) Trends Biochem. Sci. 14, 404-407; Rudd, C. E. (1990) Immunol. Today 11, 400-406. In T-cells, p56.sup.lck forms a non-covalent complex with the CD4 and CD8a. Veillette, A., Bookman, M. A., Horak, E. M., and Bolen, J. A. (1988). For this reason, p56.sup.lck is believed to aid in mediation of signals emanating from the T-cell antigen receptor through ligation of CD4 or CD8 to non-polymorphic determinants on antigen-bearing major histocompatibility molecules. Shaw, A. S., Chalupny, J., Whitney, J. A., Hammond, C., Amrein, K. E., Kavathas, P., Sefton, B. M., and Rose, J. K., (1990) Mol. Cell. Biol. 10, 1853-1862; Doyle, C., and Strominger, J. L. (1987) Nature 330, 256-259; Norment, A. M., Salter, R. D., Parham, P., Engelhard, V. H., and Littman, D. R. (1988) Nature 336, 79-81. More recently, p56.sup.lck has been implicated as a signaling component of the high affinity interleukin-2 receptor. Hatakeyama, M., Kono, T., Kobayashi, N., Kawahara, A., Levin, S. D., Perlmutter, R. M., and Tanaguchi, T. (1991) Science 252, 1523-1528.
A better understanding of the structure and regulation of p56.sup.lck and similar proteins would clearly contribute to our knowledge of early signal transduction events and a source of large quantities of purified p56.sup.lck would be useful. While early analysis of p56.sup.lck functions have been greatly facilitated by antibodies directed against this protein, immunoaffinity purification has been hampered by lack of an abundant source of enzyme. This difficulty has been addressed in part by baculovirus expression systems. Summers, M. D., and Smith, G. E. (1987). A Manual for baculovirus vectors and insect cell culture procedures, Texas A&M bulletin No. 1555, (College Station, Texas Agricultural Experimental Station and Texas A&M University), 10-39. Recent studies using a baculovirus expression system have reported significant purification of p56.sup.lck using conventional chromatography methodologies. Ramer S. E., Winkler, D. G., Carrera, A., Roberts, T. M., and Walsh, C. T. (1991) Proc. Natl. Acad. Sci. USA 88, 6254-6258; Watts, J. D., Wilson, G. M., Ettehadieh, E., Clark-Lewis, I., Kubanek, C., Astell, C. R., Marth, J. D., and Aebersold, R, (1991) J. Biol, Chem. 267, 901-907. While this approach results in purified enzyme, multiple column enzyme purification is costly, time-consuming, and requires large amounts of starting material.
Glutathione-s-transferase (Gst) is a protein well known to bind to glutathione (Smith, D. B., and Johnson, K. S. (1988) Gene 67, 31-40). Glutathione resin may be used in column chromatography. The above baculovirus expression systems, however, do not employ Gst.